A radioimmunoassay for alpha 2 mu was developed; the concentration of the protein was measured in liver, kidney, serum, and urine. Studies on the microheterogeneity of alpha 2 mu were completed. Contrary to expectation the usual hepatic profile of 5-6 species was obtained from preparation of rough endoplasmic reticulum. The hepatic protein was shown to be devoid of carbohydrate. It appears that the glucocorticoid is required for the translation of mRNA. In adrenalectomized rats the hepatic biosynthesis of alpha 2 mu was reduced 80 percent; cortisol restored its biosynthesis. The hepatic production and renal reabsorption of alpha 2 mu was studied in rats on 0 percent, 20 percent and 50 percent casein diets. The renal reabsorption of alpha 2 mu became highly efficient during protein deficiency and of low efficiency on high protein diets. Both insulin and glucagon stimulate the uptake of AIB by the liver via separate transport systems. The I/G ratio can control amino acid transport. The stimulated uptake of various amino acids was studied in rats following exposure to whole-body irradiation. Competitive inhibition studies suggest the existence of a common stimulatable transport system. BIBLIOGRAPHIC REFERENCE: Flory, W. and Neuhaus, O.W., Induced Transport of Amino Acids in Rat Liver after Whole-Body gamma-Irradiation, Radiat. Res. 68, 138-147 (1976).